JPS60229902A - Treatment of emulsion system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method of minimizing residual monomer in polymer emulsion systems.

Emulsion polymerization systems are well known for the production of many types of polymers, including rubbery styrene-butadiene polymers and acrylonitrile-containing polymers. In commercially used methods, it is desirable to minimize the amount of residual monomer in the latex. From an environmental point of view, it is desirable to minimize exposure to hydrocarbon monomers that emit malodors or otherwise pose serious health problems, but are not contaminated. From an economic point of view, a savings in free monomer of 1 to 0.5 percent is a significant cost savings to the plant. Current methods of reducing residual monomer in latex tend to be time consuming and result in reduced production. Additionally, these methods tend to be energy intensive, adding further cost to the product.

It is desirable to find faster and less energy consuming ways to reduce the residual monomer content in latex.
Most preferably, it is desirable to find a process that tends to polymerize most of the residual monomer, rather than attempting to remove it organically.

S, H, Enalund
).

Chemical Engineering Progress (Chemi)
cal Engineering Progress
), August 1981, p. 55, ``Monomer Removal from Latex.
from Latex) J presents a good discussion of some of the issues facing the industry. Removal of residual hydrocarbon monomers in the latex is limited by the rate at which the latex can be contacted with a fresh flow of fluid, usually steam, to remove this monomer. In this way,
The latex may be contacted with relatively large amounts of water vapor to ensure sufficient monomer removal. This may lead to many different types of problems such as foaming, latex destabilization or latex deterioration.

B, F, Gutdrich Company (B, F.

GOOdriCh COIII)anV> has developed several methods to remove residual acrylonitrile from aqueous polymer emulsion systems. U.S. Pat. No. 4,251,412 (issued February 17, 1981) describes a method for reducing residual acrylonitrile in latex by adding a stoichiometric amount of an amine that reacts with ACN. . U.S. Pat. No. 4,272,425 (issued June 90, 1981) discloses that after 90 percent conversion of monomer, free 11iA
describe a method for reducing the 7-crylonitrile content in latex by adding additional catalyst and comonomer in excess of cN. U.S. Patent No. 4,278.582
The specification (issued July 14, 1981) states that latex contains ammonia, ammonium hydroxide, thiol, and H2S.
Alternatively, methods have been published to reduce the residual acrylonitrile content of latex by adding alkali or alkaline earth metal carbonates, phosphates and silicates.

The present invention differs from the above techniques in that it does not contemplate adding further monomers to the latex.

The remaining methods of reducing residual monomer contemplate fluid injection, usually water vapor or inert gas, and/or passing the latex through the device at reduced pressure.

The present invention treats emulsified systems of one or more monomers of which at least 80 weight percent have been polymerized! The water vapor pressure in the surrounding environment of the emulsified system is the same as that of the emulsified system. Exposure to temperature and pressure conditions below the vapor pressure of water in the emulsion system without degrading or destabilizing the critical culm, and with a residual monomer content of 0.05 percent by weight based on the emulsion system. Processing time 1 until
at least about 0.01 parts by weight of polymer per hour
It consists of introducing parts by weight of a free radical generator into the emulsifying system.

As used herein, the term free radical generator includes the free radical generator itself and/or a combination of two or more free radical generating agents, such as a peroxide and a reducing agent. shall be taken as a thing. If more than one drug is used as a free radical generator, the amounts of drugs specified refer to the total amount of all drugs added.

The invention can be used with the following monomers: C8-12
Vinyl aromatic monomer (which may be unsubstituted or C alkyl or substituted by an alkanol residue or a chlorine or bromine atom); C conjugated diolefin: 4-8 C3-9 ethylenically unsaturated carboxylic acid; C ethylenically unsaturated aldehyde; 3-9 amide derivative of ethylenically unsaturated acid 3-9 (which may be unsubstituted or substituted at the nitrogen atom with 01-4 alkyl, alkanol, C 3-9 C alkyl of ethylenically unsaturated carboxylic acid 1-8 (this alkyl or alkanol residue may be branched or straight chain); C saturated C2-8 alkenyl or alkanol esters of carboxylic acids (the alkenyl or alkanol residues may be branched or straight chain); C ethylenically unsaturated nitriles; and 2-8 vinyl chloride or vinylidene chloride.

The method of the invention is suitable for a wide variety of homopolymers or copolymers. Water droplets are polyvinyl chloride, C1-9
Vinyl esters of saturated carboxylic acids, such as vinyl acetate,
and olefin terpolymers thereof, such as ethylene vinyl acetate, polystyrene, butadiene styrene polymers, butadiene styrene polymers containing at least one functional monomer, and acrylonitrile-containing polymers. .

Water droplets are particularly useful in situations where one or more monomers are soluble in the resulting polymer. In these cases, processing is continued until the residual content of soluble monomers in the polymer is less than 0.05 weight percent based on the emulsion system.

Preferably, the aqueous droplets are comprised of: 30 to 100 percent by weight of one or more monomers selected from C8-12 vinyl aromatic monomers, 02-8 ethylenically unsaturated di-lyl, or mixtures thereof; 04-8 conjugated diolefin 0-60 weight percent: 03-9 ethylenically unsaturated acid, 03-9 ethylenically unsaturated aldehyde, amide derivative of the c3-9 ethylenically unsaturated acid, and 03-9 ethylenically unsaturated acid. Saturated acid 01~
It is preferable to use it in a polymer emulsion system produced by polymerizing a monomer mixture consisting of 0 to 10 weight percent of one or more monomers selected from the group consisting of 8 alkyl or alkanol derivatives.

Particularly suitable vinyl aromatic monomers include styrene, alpha-methylstyrene, p-methylstyrene, chlorostyrene, bromostyrene, and divinylbenzene. A particularly suitable nitrile is acrylonitrile. Preferably, these monomers are initially present in 30 to 100 weight percent (6) of the total monomer composition.

Particularly suitable dienes are isoprene and butadiene. These monomers may be present in amounts up to about 60 weight percent of the total monomer mixture.

The initial monomer mixture may optionally contain up to 10 weight percent of functional monomer. Functional monomers include ethylenically unsaturated acids, ethylenically unsaturated aldehydes, ethylenically unsaturated amides (which may be unsaturated or substituted by C alkyl or Al 1-4 canol residues). , and C alkyl 3-9 1-8 or alkanol esters of C ethylenically unsaturated acids. Suitable functional monomers include acrylic acid, methacrylic acid, fumaric acid, itaconic acid, acrolein, methacrolein, cinnamaldehyde, acrylamide, methacrylamide, N-methylolacrylamide, N-methylol-methacrylamide, methylacrylate, Includes methyl acrylate, ethyl acrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, ethylhexyl acrylate, and ethylhexyl methacrylate.

The method of the invention is particularly useful for monomer compositions of styrene, alpha-methylstyrene, p-methylstyrene, butadiene or isoprene with one or more of the above functional monomers.

The process of the invention is carried out under temperature and pressure conditions that do not significantly degrade or destabilize the latex. At 100°C, the vapor pressure of water is 760 m of mercury.
It is 5+. Appropriate temperatures and pressures in the method of the present invention are:
50-100℃ at 92-760 mmtlg
It extends to.

Suitable temperature/pressure conditions are from about 50°C at about 92 mmHg to about 80°C at about 355 mmHg. The most preferable temperature/pressure conditions are approximately 9211ml and approximately 50°C.
to about 70°C at about 28.3 mmHg. It is important that the thermal changes during the process do not cause significant destabilization or deterioration of the latex. Those skilled in the art will be able to subject a raw latex sample to a specific temperature/temperature for a given period of time.
The sample can easily be tested to see if it results in significant culm quality degradation or destabilization when exposed to Jl and Ji-force conditions.

According to the method of the present invention, at least about 0.01 parts by weight of free radical generator per 100 parts by weight of polymer in the latex is added to the latex. The free radical generator comprises a compound or combination of compounds that decomposes to generate free radicals at the processing temperature, such as hydrogen peroxide or an organic azo or diazo compound containing up to about 12 carbon atoms. Care should be taken to choose peroxides or azo or diazo materials that decompose in a controlled manner under the conditions of use.

Suitable free radical generators may consist of oxidizing agents such as hydrogen peroxide, or redox systems consisting of organic peroxides or hydroperoxides containing up to about 12 carbon atoms and reducing agents mixed therewith. Suitable reducing agents include reducing sugars and their acid derivatives, reducing sulfur compounds,
Examples include alkali metabiite or transition metal compounds.

Suitable peroxides and hydroperoxides include hydrogen peroxide, benzoyl peroxide and t-butyl hydroperoxide.

Suitable reducing agents include iron or cobalt complexes, or reducing sugars, or derivatives thereof, such as mannitol or gluconate. The reducing agent may be a sulfur-containing compound such as an alkali or alkaline earth sulfate or bisulfite. A particularly suitable reducing agent is sodium metabisulfite.

Particularly useful free radical generator systems for use with styrene-butadiene type latexes are butyl hydroperoxide and sodium metabisulfite. The total free radical generator, preferably consisting of approximately equal parts of peroxide and metabisulfite, is about 0.0 per 100 parts of polymer in the latex.
Preferably, it is present in an amount of 8 parts by weight.

The free radical generating system is added to the latex in an amount of at least about 0.01 parts by weight per 100 parts by weight of polymer solids in the latex. The only constraint on hanging a free radical generating system above is economics. A useful upper limit for free radical generator is about 0.20 parts by weight per 100 parts by weight of polymer in the latex. The free radical generator can be used in an amount of from about 0.01 to about 0.15 parts by weight of polymer 100 in the latex. A suitable weight range for the free radical generator is from about 0.04 to about 0.08 parts by weight per 100 parts by weight of polymer solids.

The process of the present invention is not intended to involve the initial polymerization of the monomer system. Water droplets can generally be applied with a steam stripper following devolatilization of the latex.

The process of the invention can also be applied to the latex in the reactor after about 80 percent of the monomers have been converted to polymer and prior to devolatilization.

The following examples are intended to illustrate the invention and are not intended to limit the invention. Four 4 gram samples of factory-produced, devolatilized styrene-butadiene latex were processed in accordance with various aspects of the present invention or in accordance with the prior art. 124 where the sample was immersed in a constant temperature bath
I put it in 1 flask.

The flask was connected to a vacuum to control the vapor pressure above the sample. In this way it was possible to subject the sample to conditions ranging from boiling, boiling, reflux and steam injection.

A free radical generator consisting of t-butyl hydroperoxide and sodium metal sulfite was added to the system. In one experiment, the amount of free radical generator was approximately 0.05 parts per 100 parts of monomer.
Added in ``one shot'' in quantities of 1. This "one shot" addition was tested under reflux and steam injection.

The free radical generator is boiled, refluxed and under steam injection at a temperature of about 0.
It was added in an amount of 5 parts/hour. Samples of latex were periodically tested for residual styrene. A graph of percentage residual styrene (logarithmic scale) versus time in hours (linear scale) was then plotted. A plot of this data is shown in FIG. The theoretical water vapor usage was also plotted on this graph.

These graphs show that the process of the present invention is about twice as effective as conventional steam stripping in the absence of free radical generators. This improvement reduces energy consumption and significantly reduces the time required for latex stripping. Yield increases are also obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph plotting the amount of styrene remaining in latex versus time. Agent Akira Asamura

Claims (1)

Scope of Claims: (1) In a method for treating an emulsifying system of one or more single chains in which at least 80 percent by weight has been polymerized, said emulsifying group is emulsified by the vapor pressure of water in the surrounding environment. Without significantly degrading or destabilizing the system, the system is exposed to temperature and pressure conditions that are lower than the vapor pressure of the water in the emulsified system, and the residual monomer content is 0.05% based on the emulsified system. Processing time 1 until it becomes less than the weight percentage
A method as described above, characterized in that at least about 0.01 parts by weight of free radical generator is introduced into the emulsifying system per 100 parts by weight of polymer in the emulsifying system per hour. 121, FTIF is from 50 to about 100<0>C and the pressure is from about 92111113 to 760--11 g. 3. The method of claim 2, wherein the free radical generator is added in an amount of about 0.01 to about 0.10 parts by weight per 100 parts by weight of polymer per hour of treatment. (4) The method according to claim 3, wherein the free radical generator is hydrogen peroxide or an azo or diazo compound containing up to 12 carbon atoms. (5) the free radical generator is selected from organic peroxides and organic hydroperoxides containing up to about 12 carbon atoms, and the reducing agent is selected from reducing sugars, acid derivatives of reducing sugars, reducing sulfur compounds, transition metals; 4. The method according to claim 3, wherein the redox system is selected from the group consisting of compounds. 6. The method of claim 5, wherein the redox system is selected from organic peroxides or organic peroxides containing up to about 12 atoms, and the reducing agent is a sulfur compound. (7) The method according to claim 6, wherein the oxidizing agent is a C alkyl peroxide or 1 to 4 are hydroperoxides, and the reducing agent is sodium metabisulfite. (8) A method according to claim 2 in which heat and pressure conditions are maintained within the reflux condenser. (9) The method according to claim 2, wherein heat a3 and pressure conditions are maintained within the steam stripping apparatus. (+[) One or more of the monomers are from the following group: C vinyl aromatic monomers (which may be unsubstituted 8 to 12 or 01 to 4 alkyl or polyfluoranol groups or chlorine atoms or bromine C conjugated diolefin; 4-8 C3-9 ethylenically unsaturated carboxylic acid; C ethylenically unsaturated aldehyde: 3-9 C amide derivative of ethylenically unsaturated acid 3-9 ( 3-9 C alkyl of an ethylenically unsaturated carboxylic acid (which may be unsubstituted or further substituted at the nitrogen atom by a C alkyl, alkano-1-4, or alkylol residue); or alkanol ester 1-8 (this alkyl or alkanol residue may be branched or straight chain): C alkenyl 1-9 2-8 of a C saturated carboxylic acid or alkanol ester (this alkenyl or alkanol residue may be branched or straight chain); 02-8 ethylenically unsaturated nitriles; and vinyl chloride or vinylidene chloride.